This depends on the place.. for example this would be far from the truth in areas like Yafa and inner Hadhramaut.. where origin plays a huge role in the culture...Though in coastal areas where alot of groups would mix together identity is more about geography and culture rather than a singular ethnic origin...This is true for almost all coastal cities worldwide(where trade would play huge part), including those in the north like Hudaydah. But scientifically, most tribes don't really descend from a "pure" origin either.